Gas generator composition

Abstract

A gas generating composition which is excellent in a combustion efficiency and a gas output and in which amounts of residues generated are reduced in the combustion is obtained.A gas generating composition comprising (a) 5 to 40% by weight of at least one high polymer selected from the group consisting of a polyacrylic derivative resin, a polyacetal, a urea resin, a melamine resin, a ketone resin and a cellulose-based high polymer, and (b) 60 to 95% by weight of ammonium nitrate or phase-stabilized ammonium nitrate. It is suitable as a gas generating agent for an air bag of automobiles.

Description

This application is the national phase under 35 U.S.C. .sctn.371 of PCT International Application No. PCT / JP99 / 05296 which has an International filing date of Sep. 28, 1999, which designated the United States of America.TECHNICAL FIELD TO WHICH THE INVENTION BELONGSThis invention relates to a gas generating composition which is suited for an air bag restraining system of automobiles, and an inflator for an air bag using the same.PRIOR ARTAs a gas generating agent for an air bag as a passenger protecting device in automobiles, gas generating agents containing various nitrogen-containing organic compounds being safer non-azide compound fuels that replace sodium azide have been developed.For example, U.S. Pat. No. 4,909,549 discloses a composition of hydrogen-containing tetrazole and triazole compounds and an oxygen-containing oxidizing agent; U.S. Pat. No. 4,369,079 discloses a composition of a hydrogen-free bitetrazole metal salt and an oxygen-containing oxidizing agent; and JP-A 6-2...

AI Technical Summary

Benefits of technology

The gas generating composition of this invention has a low toxicity and a high safety, is easy to handle, and is excellent in a combustion efficiency and a gas output, and amounts of residues generated are reduced. Accordingly, the gas generating composition of this invention is suitable as a gas generating agent for an air bag as a passenger protecting device in automobiles. Further, since the gas generating composition of this invention has a high thermal stability, an inflator for an air bag using the same can maintain a stable performance for a long period of time and can be downsized more.

Since polyacetal (another name: polyformaldehyde) is excellent in a thermal stability and a chemical resistance and contains a large amount of oxygen (53.3% by weight), a combustibility is excellent. Further, since its melting point is close to a melting point of ammonium nitrate, it can be melted with ammonium nitrate and other additives to conduct molding. A urea resin and a melamine resin are, like a polyacetal, excellent in a combustibility, a thermal stability and a chemical resistance.

Examples of the combustion accelerating agent as component (c) can include bitetrazole metal salts and non-metal salts such as bitetrazole sodium salt, bitetrazole potassium salt, bitetrazole ammonium salt, bitetrazole calcium salt, bitetrazole manganese salt, bitetrazole zinc salt, bitetrazole cobalt salt, bitetrazole guanidine, bitetrazole melamine and the like. Of these, bitetrazole potassium salt is preferable because the effect of accelerating the burning rates of components (a) and (b) is greater than that of the accelerating agent such as potassium perchlorate, calcium nitrate or the like in the same amount and the amounts of solid residues generated after the combustion are reduced. In addition, phase-stabilized ammonium nitrate is formed with ammonium nitrate as component (b) and the volume change of the gas generating composition can be prevented in the use temperature range.

When the gas generating composition of this invention is a three-component type of components (a), (b) and (c), the content of component (a) is preferably between 1 and 40% by weight, more preferably between 5 and 30% by weight, the content of component (b) is preferably between 60 and 94% by weight, more preferably between 65 and 90% by weight, and the content of component (c) is preferably between 0.5 and 15% by weight, more preferably between 3 and 15% by weight. When the content of component (c) is in the above-described range, a molding strength is good. When a bitetrazole metal salt is used as component (c), amounts of combustion residues can also be reduced.

The gas generating composition of this invention can be applied to an air bag inflator for a driver side, an air bag inflator for a passenger side and a side inflator. Further, it can be applied to a hybrid inflator. With respect to the air bag inflator of the driver side, a gas output is high, and amounts of residues generated are reduced, so that a filter for filtering residues can be reduced to downsize an inflator. With respect to the hybrid inflator, the gas generating composition of this invention has an oxygen balance which is 0 or close to 0, so that an oxygen-free compression gas can be used.

Problems solved by technology

Thus, in either case, there is a problem that a gas output is low.

Further, large amounts of residues are generated in the combustion.

Accordingly, when residues generated are released as such from an inflator, high-temperature liquid or solid residues might damage a bag and a bag might be separated from an air bag module or burned.

In addition, it is sometimes harmful in breathing of passengers.

However, this method is against downsizing of an inflator and reduction of its weight, and also increases the production cost.

Besides, the composition containing phase-stabilized ammonium nitrate and nitroguanidine has a high initiation sensitivity, which is problematic in the safety of the production of the gas generating agent.

Moreover, the gas generating composition made of ammonium nitrate, tetrazoles and a metal oxide, disclosed in JP-A 10-72273, is hard to mold because of the absence of a high polymer, and cannot endure a volume change when a phase of ammonium nitrate is changed, making it difficult to control combustion of the gas generating agent after the lapse of a long period of time.

However, these gas generating agents are problematic in that a large amount of hazardous carbon monoxide is generated in the combustion.

Further, since a burning rate is low, it is difficult to simply apply the same to gas generating agents for an air bag of automobiles.